BIO 183 1st Edition Exam 2 Study Guide Chapters 6 8 Chapter 6 Energy and Metabolism Terms and Definitions Catalyst substance that speeds up a chemical reaction by lowering the activation energy What is Metabolism Metabolism is the sum of all biochemical reactions in a cell It includes two types of reactions anabolism and catabolism Anabolic reactions require energy to build up molecules dehydration Catabolic reactions break down molecules and release energy hydrolysis What is Activation Energy Activation energy is the extra energy needed to destabilize existing chemical bonds and initiate a chemical reaction The rate of exergonic reaction depends on the activation energy and it can be increased by 1 increasing the energy of reacting molecules or 2 by lowering activation energy What are enzymes What are their functions Enzymes are agents that carry out most of the catalysis in living organisms Most enzymes are proteins that may be found in the cytoplasm or attached to cell membranes and organelles They alter the activation energy of a reaction An enzyme consists of active sites pockets for substrate binding so that when it binds to a substrate it becomes an enzyme substrate complex What do enzyme cofactors do cofactors are chemical components that assist enzyme function These can be metal ions that are often found in the active site participating directly in catalysis Cofactors are called coenzymes if they are nonprotein organic molecules Vitamins are example of coenzymes What is the role of inhibitors What is the difference between their types Inhibitors are substances that bind to enzymes and decrease their activity There are 2 types competitive compete with substrates for active sites noncompetitive bind to enzymes on allosteric sites other than active sites which affect the shape of enzymes so that they can bind to substrates What is a biochemical pathway A biochemical pathway is a sequence of reactions that occur in the cell It is the organizational unit of metabolism In such pathways the product of one reaction becomes the substrate for the next Figure 1 Biochemical pathway What is a feedback inhibition Feedback inhibition is when the end product of a biochemical pathway binds to an allosteric site on the enzyme that catalyzes the first reaction in the pathway It shuts down pathway so raw materials and energy are not wasted What are the major factors that affect the function of an enzyme Temperature pH substrate concentration Salt concentration inhibitors Chapter 7 How Cells Harvest Energy Terms and Definitions Electrochemical gradient is a gradient of electrochemical potential usually for an ion that can move across a membrane ATP Adenosine triphosphate is used to power most of the cell s activities ATP synthase is the enzyme that synthesizes ATP using energy from a proton gradient H NAD nicotinamide adenosine dinucleotide acts as a cofactor that helps enzyme catalysis What is the difference between Autotroph and Heterotroph Organisms can be classified based on how they obtain energy Autotroph able to produce their own organic molecules through photosynthesis Heterotroph live on organic compounds produced by other organisms What is a Redox reaction What is the difference between fermentation Aerobic and Anaerobic respiration Redox reaction is the pair of oxidation electron loss and reduction electron gain reactions Oxidation reduction reactions play a role in the flow of energy through biological systems For example cells use NAD as a cofactor to carry out redox reactions NAD accepts 2 electrons and 1 proton to become NADH NADH can then donate electrons to other molecules At the end of the process high energy electrons from the initial chemical bonds lose much of their energy and are transferred to a final electron acceptor Aerobic respiration is when the final acceptor is oxygen Anaerobic respiration is when the final acceptor is an inorganic molecule other than oxygen Fermentation is when the final acceptor is an organic molecule How do electrons transport work ATP is generated when electrons transfer from one energy level to another Energy is released each time electrons fall to lower energy levels in steps What are the types of electron carriers Electron carriers are used in energy metabolism Different forms of these carriers can be used 1 Soluble carriers move electrons from one molecule to another 2 Membrane bound carriers form a redox chain 3 Carriers move within membrane These carriers can be reversibly oxidized or reduced NAD is one of the most important electron and proton carrier How is ATP synthesized ATP is synthesized by two different mechanisms 1 Substrate level phosphorylation ATP is formed by transferring a phosphate group directly to ADP from a phosphate bearing intermediate or substrate A molecule of phosphoenolpyruvate PEP possess a high energy phosphate bond similar to the bonds in ATP When a phosphate group from PEP is transferred to ADP the energy in the bond is conserved and ATP is created 2 Oxidative phosphorylation ATP is synthesized by the enzyme ATP synthase using energy from a proton H This gradient is formed by high energy electrons from the oxidation of glucose passing down an electron transport chain Depleted energy from electrons are then donated to oxygen The cell carries out a series of enzyme catalyzed reactions that remove energetic electrons These electrons are then used in an electron transport chain and passed to the intermembrane space Since it is an aerobic respiration the final acceptor is O2 and the resulting proton gradient provides energy for ATP synthase to phosphorylate ADP to ATP What are the stages for glucose oxidation 1 Glycolysis Occurs in the cytoplasm Consists of 10 step biochemical pathway Converts glucose 6 Carbons to 2 pyruvate 3 Carbons Produces 2 ATP molecules for each pyruvate by substrate level phosphorylation Reduces NAD to 2 NADH for each pyruvate Recycling NADH to continue respiration by a Aerobic respiration Produces ATP O2 is the final electron acceptor b Fermentation occurs when O2 is not available organic molecule is the final acceptor Fate of pyruvate when oxygen is present aerobic pyruvate is oxidized to acetyl CoA which enters the Krebs cycle when oxygen is not present fermentation pyruvate is reduced in order to oxidize NADH back to NAD Fermentation oxidizes NADH to NAD so it can be re used in glycolysis 2 Pyruvate oxidation Occurs in the mitochondria eukaryotes or plasma membrane prokaryotes